The present invention relates to a regulating and energizing circuit for the field coil of a brushless alternator in which the primary of a rotary transformer is supplied with direct current pulses to effect energization of the field coil with the pulses being modulated to control the field current in response to the output voltage of the alternator.
The art discloses oscillators to provide pulses to effect energization of the field coils in generators and alternators. U.S. Pat. No. 3,374,419 energizes the field coil of a rotating generator with uni-directional pulsating current at a high frequency current. Similarly, U.S. Pat. No. 3,631,258 discloses circuitry for pulsating the field coil at a rate approximately 10 times gerater than the off/on frequencies of the regulator, for example, 1,000 Hz.
In addition, the art has recognized the use of a pulse generator to supply current pulses to a center tapped transformer whose secondary windings operate to supply DC current to a load, see U.S. Pat. No. 3,526,823, and the use of DC current pulses derived from an oscillator which are applied to the center tapped primary of a rotary transformer in a brushless alternator, see U.S. Pat. No. 3,617,857. The pulses are at a frequency greater than the on/off regulation of the regulator in response to the output voltage of the generating machine. Regulation is accomplished by providing constant frequency pulses from an oscillator and turning the oscillator fully on and fully off in accordance with the during machine output voltage. In the circuit of U.S. Pat. No. 3,526,823 current pulses of uniform width are supplied at a variable frequency to energize the center tapped primary of a transformer with direct current pulses that flow in opposite direction in the primary to induce current in the transformer secondary for supplying DC current to a load. U.S. Pat. No. 3,378,708, utilizes a static type multivibrator circuit as a free running oxcillator to the supply energizing pulses to an alternator coil with the oscillator frequency and pulse width being varied in dependency on alternator output voltage.